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Ideas to prevent Failures of Solid State relays

K

karthik

Jan 1, 1970
0
I am using Solid state relays to On/Off heaters so as to control
temperature.
In case if heaters get short,immediately the Solid state relays ( SSR )
also gets short and
I need to change new one.Even though I have Fuse protection the SSR and
Fuse gets blown.
Since the Cost of SSR is high,I have so many troubles.

So any one Please suggest some ideas to prevent SSR failure.Is there
any protection like
Varistors , RC circuit to prevent this
 
P

Pooh Bear

Jan 1, 1970
0
karthik said:
I am using Solid state relays to On/Off heaters so as to control
temperature.
In case if heaters get short,immediately the Solid state relays ( SSR )
also gets short and
I need to change new one.Even though I have Fuse protection the SSR and
Fuse gets blown.
Since the Cost of SSR is high,I have so many troubles.

So any one Please suggest some ideas to prevent SSR failure.Is there
any protection like
Varistors , RC circuit to prevent this

You answered your own question The SSRs are broken when the heater is a
short.

Fix the problem with the heaters !

A super fast fuse combined with derating of the SSRs may help too.

Graham
 
J

Jamie

Jan 1, 1970
0
karthik said:
I am using Solid state relays to On/Off heaters so as to control
temperature.
In case if heaters get short,immediately the Solid state relays ( SSR )
also gets short and
I need to change new one.Even though I have Fuse protection the SSR and
Fuse gets blown.
Since the Cost of SSR is high,I have so many troubles.

So any one Please suggest some ideas to prevent SSR failure.Is there
any protection like
Varistors , RC circuit to prevent this
yes, SSR's can short if the load they are
driving shorts how ever, in cases like we have
at work we have line fuses that are rated much
lower than what the SSR is and thus you would think
they shouldn't short but they do at times.
the problem we had at work was not so much the
load but the inductive energy and unbalanced load
effects that multiply the voltage above the limits
of the SSR.. that is most likely your problem.
we solved our problem by running the lines to the heaters
spaced apart from other lines and used a TVS on each SSR
brick.
now if there is a loose connection or short, only the
fuse blows if needed.
 
P

Phil Allison

Jan 1, 1970
0
"Jamie"
the problem we had at work was not so much the
load but the inductive energy and unbalanced load
effects that multiply the voltage above the limits
of the SSR.. that is most likely your problem.


** If an SCR or Triac is overvoltaged by a spike or similar (in the off
state) then it simply triggers on for the rest of the cycle. This is not
destructive to the device.

So it is not destructive to SSRs either.





.......... Phil
 
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